# math

i really need help, i have no idea how to answer this question !

A stone is thrown off a cliff. it reaches a maximum height of 30m after 2 seconds, then falls into the water below. it hits the water after 5 seconds

a) how high above the water is the cliff ( The maximum height is relative to water level )

b) what is the ' second zero' and what does it mean

i really appreciate the help

1. 👍 0
2. 👎 0
3. 👁 66
1. first, we solve for the initial velocity from the formula of the maximum height:
h,max = [(vo)^2]/(2g)
where
vo = initial velocity
g = acceleration due to gravity = 9.8 m/s^2
substituting,
30 = [(vo)^2]/(2*9.8)
vo = sqrt(588)
vo = 24.25 m/s

(a) note that the motion of the stone is uniformly accelerated motion, thus we can use the formula:
h = ho + (vo)*t - (1/2)*g*t^2
where
h = final height
ho = initial height
t = time
since the stone is thrown from the cliff, and making the water as reference, ho = the height of cliff, and h = 0. substituting,
h = ho + (vo)*t - (1/2)*g*t^2
0 = ho + (24.25)*(5) - (1/2)*9.8*(5^2)
0 = ho - 1.25
ho = 1.25 m

(b) ..sorry but i don't know what second zero means~ ^^;

anyway, hope this helps~ :)

1. 👍 0
2. 👎 0
posted by Jai

## Similar Questions

1. ### GRAMMAR - MT

Proofreading. Clean up the following sentences by identifying and correcting misspellings and misused/incorrect words. QUESTION: 1.Urolithiasis is another name for one of the following: uretral stone, kidney stone, or renil stone.

asked by Leslie-To:Writeacher on July 16, 2011
2. ### English

To answer the question below, use an idea that you generated in Part 2 of Lesson 2 or come up with a new idea. In the text box provided below indicate the following; The writing idea The kinds of questions you will be writing

asked by Nannielee on February 14, 2012
3. ### maths

My kids are stuck on this they've no idea what to do and I can't help them out either! Darren throws a stone from the top of a vertical cliff into the sea below. The trajectory of the stone can be modelled by the quadratic

asked by elizabeth on April 20, 2011
4. ### machanics\

can u tell me what formula i should be using to answer this question? If a stone falls past a bird on a ledge moving at 4 m/s, how fast will the stone be movingjust before it hits the ground below 9 seconds later? A. 92.2 m/s B.

asked by me on May 3, 2010
5. ### machanics

can u tell me what formula i should be using to answer this question? If a stone falls past a bird on a ledge moving at 4 m/s, how fast will the stone be movingjust before it hits the ground below 9 seconds later? A. 92.2 m/s B.

asked by me on May 2, 2010
6. ### physics

An inquisitive physics student and mountain climber climbs a 50.0m high cliff that overhangs a calm pool of water. He throws two stones vertically downward, 1.00 s apart, and observes that they cause a single splash. The first

asked by Anonymous on March 30, 2016
7. ### English

1. Part A-which pair of words best describes the speaker's attitude toward elements of nature in "wind and water and stone"? A. ignorant and uncaring B.joyful and loving C.angry and scared D.calm and accepting*** Part B-Which line

asked by Anonymous on February 15, 2018
8. ### Science

Miguel is skipping rocks across the surface of a lake. After he throws it, each stone goes through the following motions: I. the stone moves toward the water II. the stone hits the surface of the water and bounces off III. gravity

asked by Lovely Mallory on March 20, 2013
9. ### physics

A stone with mass m = 2.3 kg is thrown vertically upward into the air with an initial kinetic energy of 190 J. The drag force acting on the stone throughout its flight is constant, independent of the velocity of the stone, and has

asked by Katie on February 22, 2012
10. ### PSU

A 2.3kg stone is thrown from ground directly upward. the maximum height reached by the stone is 45m. Neglecting air resistance, a) with which initial speed was the stone thrown? b)what is the flight time of the stone until it hits

asked by Abdelaziz on October 26, 2016
11. ### physics

A boy drops a stone-A, down from a cliff 480 meters high, next he throws a stone-B, 1 second later - at what initial velocity was the stone-B be thrown so as to meet the stone-A on ground at the same time? g=10 m/s2.

asked by alex on June 21, 2011

More Similar Questions